[en] The invention may be used to improve the design of a pool type liquid metal cooled fast reactor. There is a vertical main tank containing components of the primary cooling circuit, and an internal tank enclosing the core. The invention is aimed at increasina the stability of liquid metal thermohydraulic flow inside the main tank of power reactors (1000 MWe and more) that must improve the reliability. The aim is achieved by attaching splitters to the main tank wall and locating the upper part of the lateral wall of the internal tank below the top of the core and above the level of the heat exchanger outlets. In this case the external side of the lateral wall is bent downward and attached directly to the main tank